We utilize spatial and angular diversity to achieve speckle reduction in laser illumination. Both free-space and imaging geometry configurations are considered. A fast two-dimensional scanning micromirror is employed to steer the laser beam. A simple experimental setup is built to demonstrate the application of our technique in a two-dimensional laser picture projection. Experimental results show that the speckle contrast factor can be reduced down to 5% within the integration time of the detector.

Polymer nanocomposite has shown great potential and impact on a broad range of techniques since its properties can be tailored by nano-fillers. This paper reports a polymer nanocomposite with enhanced electro-mechanical performance by mixing TiO2 nanoparticles into polydimethylsiloxane. Nanocomposites with particle concentration up to 30 wt% were prepared. High energy ball milling and polyether-modified silicone dispersant were used to suppress the agglomeration and ensure a stable dispersion. Properties of the nanocomposites, i.e. elastic modulus, response time, dielectric constant and optical transmittance, were tuned by modifying the particle concentration. Optimized electro-mechanical properties were observed at 5 wt% TiO2 particles. This nanocomposite was applied to a MEMS spatial light modulator, which was fabricated using micro-machining technology. The device was driven by a 200 V dc voltage and had a response time of 6 µs.

Speckle reduction by moving diffuser has been previously studied in display systems with coherent light sources, such as lasers. In this Letter, we propose a motionless diffractive optical element (DOE) for speckle reduction. The DOE was designed based on finite-element method simulations, fabricated using micromachining technology, and characterized for despeckle efficiency. Experiments using a DOE with two gratings have indicated that the speckle was suppressed to 50%, which shows fair agreement with theoretical analysis. With some modification of this DOE, the speckle noise can be reduced to 10% according to the theory.

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